s3 OneFS: Add kernel oplocks implementation

s3 OneFS: Add kernel oplocks implementation

A few functions in oplocks_onefs.c need to be accessed from the onefs
vfs module.  It would be ideal if oplocks were implemented at the vfs
layer, but since they aren't yet, a new header is added to
source3/include to make these functions available to the onefs vfs
module.  oplocks_onefs.o doesn't need to be linked into the onefs vfs
module explicitly, since it is already linked into smbd by default.